Shock absorbers and damping systems are used for damping of the relative movement between the wheel and the chassis of a vehicle, such as a car, a motorcycle or a bicycle. A conventional shock absorber normally comprises a working cylinder filled with a damping fluid, such as hydraulic oil or gas, and a piston arranged in the cylinder. The damper may then be arranged to move telescopically between the vehicle chassis and the wheel. The movement of the wheel and vehicle is thus damped by the piston moving in the cylinder against the resistance of the fluid, which further causes damping fluid to move in the damping cylinder. In the specific case of a bicycle, or mountain bike, dampers may be arranged in a front fork arrangement and/or between the driver and the rear part of the bike, in either case damping impacts and vibrations with respect to the driver.
Further, the shock absorber may comprise means for controlling the damping force exerted due to the flow of fluid through the damper. Such means may include different types of valve arrangement. In high end dampers, the amount of fluid allowed to pass for example through the piston and therefore the characteristics of the damper may be controlled by using manually or automatically adjustable valves of different types.
It is also known to use several flows and/or valve arrangements comprising several valves adapted to control the flow at different speeds. For example, a so called high-speed valve may be used to control the flow through the piston at high speed, whereas a so called bleed-flow may be used to allow for a flow between working chambers at lower speed when the main flow/high speed valve is closed.
For applications in the field of mountain bikes, the special situation arises that efficient damping is associated with the problem of the damping system absorbing pedalling energy from the rider. Thus, it may be desirable during some riding conditions, for example when travelling uphill, to lock the damping system such that no pedalling energy is lost to the damping system. This is sometimes referred to in the art as a so called lock-out of the damping system. Such lock-out states are preferably activated by the driver when desired and aims at balancing the need for damping versus the need for efficient pedalling, depending on the riding conditions.
For example, WO05052406 discloses an example of a lock-out system for a bicycle. The system comprises a lock-out valve operable by the rider combined with a blow-off valve.
WO0115964 discloses another example of a lock-out system. The system comprises a manually adjustable lock-out valve and an adjustable blow-off valve for controlling damping characteristic suitable for different driving conditions and a piston with a primary and a secondary channel. The blow-off valve is adjustable between a locked and an open position in order to allow or prevent a flow through the secondary channel.
However, the use of two adjustable valves greatly increases the complexity of the operation of the system for the rider, and in order to achieve a locked, or stiff, shock absorber when desired, the rider must adjust both valves into a locked or closed state.
The inventors of the present invention have identified a need for an improved shock absorber for a vehicle. There is a need for a shock absorber which is adjustable between different states of operation and which is easily adjusted between for example a locked state and a state wherein damping is provided to the vehicle.
Thus, an object of the present invention is to provide a shock absorber with adjustable damping properties. A further object is to provide a shock absorber which has an efficient lock-out state allowing the use of all pedaling energy for forward propulsion. Yet another object is to provide a shock absorber which is easy to use and which provides for a simple and reliable adjustability of the damping properties.